A robot system for controlling an industrial robot has a portable teaching operation portion (also referred to as a pendant) which a worker carries, for example, when a teaching operation is performed, in addition to a control portion for controlling an operation of the robot. Hitherto, a composite cable (hereinafter called a cable) which uses a twisted pair wire or an optical fiber as a signal transmission path and which includes a power supply line used to supply electric power to the teaching operation portion, has been used for transmission of information between the teaching operation portion and the control portion.
A diagram illustrating the configuration of a conventional robot system described in Patent Document 1 as an example is shown in FIG. 7. In FIG. 7, reference numeral 101 designates a robot. Reference numeral 102 denotes a control portion which controls an operation of the robot 101. Reference numeral 103 designates a portable teaching operation portion. Reference numeral 104 denotes a cable through which information regarding an operation button, an emergency stop, and the like is transmitted between the control portion 102 and the portable teaching operation portion 103. A detail illustration of the portable teaching operation portion 103 is shown in FIG. 8. In FIG. 8, reference numeral 105 designates a substantially T-shaped casing. Reference numeral 106 denotes a hand portion which a worker grasps. A keyboard (or a keysheet) 107 to be operated when a teaching operation is performed, an LCD display 108 constituted by a liquid crystal panel, on which teaching data and information regarding the position of the robot and the like are displayed, and an emergency stop switch 109 (corresponding to the emergency stop operation section) are provided on an operation surface of the casing 105. An end of the cable 104 is connected to the casing 105.
When a worker depresses the emergency stop switch 109, emergency stop information is transmitted to the control portion 102 through the cable 104. The control portion 102 interrupts power supply to drive motors (not shown) of the robot 101 to thereby forcibly stop an operation of the robot 101. Consequently, the control portion 102 can surely stop an unexpected operation of the robot.
The aforementioned conventional robot system needs to perform, when a worker carries the portable teaching operation portion 103, a teaching operation by simultaneously trailing a thick and heavy cable. Thus, the aforementioned conventional robot system has problems that the worker has a heavy burden, and that the degree of freedom of motion at the time of teaching is constrained. Consequently, it has been strongly demanded to unwire the cable 104 connecting between the control portion 102 and the portable teaching operation portion 103. For example, Patent Document 2 describes means for implementing an emergency stop function in a robot system configured so that the portable teaching operation portion, which has an emergency stop operation section for bringing a robot by interrupting supply of electric power to a drive motor of a robot, and the control portion for controlling the robot communicate with each other through radio waves.    Patent Document 1: JP-A-2000-280193 (Page 7, FIGS. 1 and 2)    Patent Document 2: JP-A-2004-148488